Control and Measurement of Unintentional Electromagnetic Radiation

CHAPTER 6

CONTROL OF CIRCUIT-CURRENT RADIATIONS

6.1 INTRODUCTION

To control unwanted radiations from circuit currents, it is clear that meas|E_n| must be minimized. The individual parameters that must be adjusted are clearly identified in the expressions given for meas|E_n|.

As previously determined, values of meas|E_n| to be expected from small, medium-length, and long-length rectangular circuit currents can be calculated with the following equations. For small and medium-length circuits with source voltages such as those discussed in Chapters 4 and 5

and for long circuits with those same source voltages.

The second of these equations, in each case, results because Z_o = 120π ohms, c = 300×10⁶ meters/second, and the assumed measurement distance is d = 10 meters. The remaining parameters with which meas|E_n| can be reduced are

V_p, the amplitude of v(t), in volts

D_n, the transition factor of v(t), in megahertz

Z_n, the impedance of the circuit, in ohms

W, the width of the circuit, in centimetres

These four parameters, V_p, D_n, Z_n, and W, and how they can be adjusted to minimize meas|E_n| are the primary topics of discussion in this chapter. Each of these parameters is examined in order of increasing importance based on the extent to which each is usually adjustable. The order of discussion ...